Ooh! That's actually going to be one of the biggest butterflies in this timeline. I plan to have the Ottomans win the war (think Nasirissimo's With the Crescent Above Us) but I'm probably going to do an indirect update about that; maybe a newspaper article or a diary entry. I'm damn clueless on writing war updates, especially on European wars.
With the Ottomans winning the war and returning to Great Power-(ish) status, I can see Abu Bakar establishing closer relations with Sultan Abdul Hamid to ensure Johor's independence (though it's going to be a fine line with British Singapore close by. A visit to Queen Victoria could resolve that, or not) and provide another outlet for the sultanate's exports.
The problem with the Ottoman project their power so distant to home is that even if they win the war with the russian and get to buy time, they still have tons of problem at home as their north african possession are de facto independent and are the target of Italy, France and UK; they still own to the european a lot of money to modernize and they need more to continue the job, the massacre of christian during the war put the pubblic opinion against the Porte so even if victorious the Concert will demand some concession towards the Balkans nations under nominal Ottoman authority.
So getting involved on a so distant land can be seen as a waste of limited resources, expecially if the British are not very pleased of this move.
PS: i like Nassirissimo TL (as it's well reserchead and enterteing) but honestly when he wrote about the OTtoman Empire tend to give them a lot of free pass